Topic: Electrical Odyssy: Now TORMENT [Updated]

[TwoTired]

I recommend you 1,  find out why your field coil resistance is an ohm higher than it should be when starting out.  And 2, why it climbs to 10 ohms after steady use.  I have little doubt this why your alternator weakens with use.

Wildo. I also want to double check, just to make sure, that my readings on the field coil are correct. I didn't realize that 10 ohms would be that far out of spec.

FYI. The stock regulator inserts 10 ohms into the field coil circuit (to reduce the alternator output), when it believes the battery is fully charged.

Happy Hunting those villainous ohms!

[burmashave]

I think I may have found the villains, at least I hope so. I pulled the covers and tested the wires, especially the resistance between the white wire at the regulator against the green wire at the rectifier (both field coil wires).

These wires have no connectors between the component and the coil, although each wire has a solder joint behind the gearshift cover (where the bullet connectors were). The wires from the reg. & rect. to that solder joint are new, but the wires from the coil to that joint are original. I would have extended the new wires further; however, I was afraid that standard wire insulation would not handle the heat inside the alternator cover.

Visually, the wires look good, and I could not get resistance to change at all from 7.8 ohms while moving the wires all about. I have a service bulletin that states that 7.2 ohms is the specification for the field coil, so I would think 7.8 isn't too bad.

I then took my heat gun and started heating the coil. The resistance started going up as soon as the heat began to spread. It slowly rose to 8.6 ohms before I turned the gun off. At that point, the coil was hot, but not nearly as hot as engine covers get. By the way, I heated the center core of the coil as opposed to heating the wires directly.

I will fully admit that I could still be missing something, but it appears to me as if the coil has gone bad. We've got a really good bike boneyard near me, so I'm going to see about getting one there (and test it before I buy it).

[burmashave]

I picked up a used coil for $50 at the boneyard. The resistance on it is 7.1 ohms. I installed it yesterday. I'm hoping I'm out of the woods, but the numbers I've gotten confuse me a bit.

On a cold start, with a battery just off the charger (battery is about a month old), I get some really good numbers:

Voltage @ RPM: Cold Start w/Freshly Charged Battery

RPM		Voltage
0		12.24
2.0		12.48
3.0		13.24
3.5		13.30
4.0		13.30

I took off on a ride, and at first, the charging system had more voltage than before. My LED voltmeter runs about 1/2 volt lower than a multimeter at the battery, and accounting for this, the bike ran consistently above 13.5 volts for about the first 20 miles. After that, it dropped to a consistent 12.5-13.5 volts for the rest of the ride (100 more miles).

I put the multimeter back on it when I got home:

Voltage @ RPM: After 125 Mile Ride

RPM		Voltage
0		12.12
2.0		12.25
3.0		12.50
3.5		12.47
4.0		12.58

So, I'm hoping that the reason why the voltage decreased during the ride is that I started with a really fresh charge? Even if that's the case, I wonder why the second set of numbers shows such a small increase from idle to 4k RPM?

The good news is that according to my LED gauge, the voltage was rock solid above 12.5 volts for the whole ride (except in villages or while using the high beam).

Now, I'm wondering if the stator might also be weak. Essentially, I think I have replaced almost all of the other components in the charging system. :-(

[TomC]

Hi Burnashave
     I have seen over 14.5 volts across the battery of my CB400F1 with a 55/60 watt head light today. Actually the reason I started playing with the voltage regulation was that I was seeing over 15 volts.
     I am current running a digital voltmeter wired to the battery. I can see changes of a hundredth of a volt. Also I have an analog voltmeter between the white wire at the regulator and ground. This meter tells me if the regulator is trying to control the voltage.
     I would think that with all you have done with LEDs your 750 is drawing less current that my 400. A 750 should produce much more power that a 400. About 75 watts more.
     I would suggest that you need to wire volt meters as I have. See what is happening as you go down the road.
          TomC in Ohio

[TwoTired]

A fully charged wet cell battery should read 12.6V after a two hour rest, off the charger.

Why does your "fully charged" battery read less than that?

Cheers,

[Jerry Rxman Griffin aka MuthaF'er]

Burma,

What you're going through sounds like my situation. Drove me crazy! I too have Dyna 3ohms with halogen headlight but Dyna III. Cleaned every friggin connector. The only things I haven't done are replace my ignition switch and put the NOS harness in that I'm sitting on for the restore. I have replaced the harness once with another used one. I'm lucky to pull 13.5V at rpms. No way can I get 14V or 14.5V. Couldn't do it with my electronic reg/rect that I fried trying to resolve this dilemma. Can't do it with the stock reg/rect replacements. No way. I wish I had a NOS set of coils to swap out just to see the difference. Thats pretty much it for me and I'm living with it. Stay out of heavy city stop and go traffic and I'm fine. Perhaps a headlight switch could be useful but I like the visibility the headlight creates. My solution is a Battery Tender so I'll at least have the voltage when I leave. If it gets dire my headlight is fused which I can remove if it's daylight.  

Good luck dude. I'm believing that 14.5V with Dyna 3ohms is a holy grail that I can not achieve. Don't need 14.5V anyway. The haolgen is brighter than the standard bulb at 12.5V or 13V. Keep up and let me know if you pull it off.

[burmashave]

A fully charged wet cell battery should read 12.6V after a two hour rest, off the charger.

Why does your "fully charged" battery read less than that?

Cheers,

Sorry, I should have specified that the voltages @ zero RPM are with the ignition switched on.

Good luck dude. I'm believing that 14.5V with Dyna 3ohms is a holy grail that I can not achieve. Don't need 14.5V anyway. The haolgen is brighter than the standard bulb at 12.5V or 13V. Keep up and let me know if you pull it off.

Jerry, I may actually be pretty happy with the performance I'm getting if I'm topping out. I was almost always over 12.5 volts, so I should be pretty good if that's what I can get. At this point, I just really want to make sure all is well and that things are optimized.

     I am current running a digital voltmeter wired to the battery. I can see changes of a hundredth of a volt. Also I have an analog voltmeter between the white wire at the regulator and ground. This meter tells me if the regulator is trying to control the voltage.

That's a good idea. I have a spare MM, and prolly could rig up something similar.

[eurban]

Either later today or over the weekend I will take some measurements of my charging system.  As I mentioned, it performs well in spite of the added draw of the Dyna III, 3ohm coils and a halogen headlight.  I will confirm what I have tested previously (13volts+ at idle, 14+ above 2500or3500?).  I have a quality digital multimeter and can perform comparison tests if you like.  I won't be pulling off the engine covers but can test up at the RR and rectifier connectors.  Let know what would be helpful. TT? RX? Burma?. . . . .

[eurban]

Made some measurements this afternoon:

Bike is a 78 750K with: Halogen headlight, other lights LED, Dyna III, Dyna 3ohm coils, optimized stock wiring harness and fuse box, new ignition switch / handlebar controls, OMP solid state regulator, aftermarket (brand?) rectifier, 2 year old sealed battery.

6.8 ohms white wire to ground resistance measured at gang connector (BR,G,W,Y,Y,Y,LGR) behind/above fuse box. I used the main ground strap for the ground and all connectors remained connected.  This should be the field coil resistance NO?

Battery voltage after 1 hr off of the Tender, ignition off: 12.7 volts

I couldn't take the bike for a ride so with a coldish motor, idle RPM measurement was difficult:

1.2 K RPM: 12.6 volts
2.0 K RPM: 13.25 volts
3.0 K RPM (and above): 14.75 volts

Numbers for idle and 2k were a bit lower than I remember testing before but perhaps my memory is failing.  A cold engine that was reluctant to run smoothly below 2k didn't help with testing and perhaps affected these numbers.

If we are comparing apples to apples with our meters and our particular setup's current useage then your charging system is not functioning correctly.  You do have the Dyna 2k ignition but I can't imagine that it would put you so far over the threshold.  Is it speced to draw significantly more amps than the III??  What is the wattage of your headlight?  As TT mentioned, your field coil resistance seems to be too high. . . Bottom line is that it doesn't seem to me that you should accept things as they are.  Something is amiss and after all your work, you should find the fault (s) and correct them.  You too RX

PS: do you have a good main ground connection?  Powdercoat and engine paint can do a good job of insulating the main chassis ground connector . . .

[burmashave]

Hey thanks, eurban. Something is definitely wrong. Before seeing your post, I did the same thing on my bike on a cold start, and got numbers close to yours:

Voltage @ RPM: Cold Start

RPM		Voltage
0 (ign. off)		12.72
0 (ign. on)		12.25
2.0		13.00
3.0		13.70
3.5		14.50
4.0		14.72

Given that I have made no changes since my last readings above, I still have an intermittent problem or problems. I am psyched to see that my bike will produce that voltage, so I just need to figure out what is intermittently failing.

My suspicions run toward the stator. Perhaps, like the field coil, it is running weaker when hot. Alternately, I suspect wiring or the voltage regulator, although the regulator is nearly new.

I'm going to try to rig up dual MM's to use while running as suggested by Tom. It'd be telling to know what's happening to the voltage across the white voltage regulator wire when the voltage output declines.

On the other hand, I won't be able to do anymore testing until next week because I tore my forks down today before I realized that I don't have all the parts I need for reassembly.  Grrrrrrrrrrrrr.... (I didn't realize that ServiceHonda had split the items into two shipments).

[TomC]

Hi Burmashave
     I went to Harbor Freight Tools to get two of the $2.99 multi meters that are on sale. It is about a 45 mile round trip. The trip starts and ends in the country and is in the city in the middle. At 4000rpm I saw from 12.5 to 14.5 over the course of the trip. The voltage regulator started cutting in about 0.1 miles from my house on the way to Harbor Freight and maybe a mile from getting home. Clearly all the sitting all traffic lights kills the battery and it takes time at speed to recharge the battery.
     My CB400F1 is a worst case. At idle it draws about 6amps from the battery. At speed it can put about 3amps into the battery unless I use the turn signals or the brake light. I would say I need at least 3 minutes at speed for each minute at idle.
     I have checked the  output of my alternator at about 5,000 rpm and it is producing about 160 net watts. One of these days I will try this again with a switch to bypass the voltage regulator. When I was checking the alternator output the voltage regulator would cut in and reduce the alternator output.
          TomC in Ohio

[burmashave]

I think I've finally got it licked. After I replaced the coil, the charging/electrical system was still having thermal failure. The hotter my bike got, the less charging I had. It was more of a general than a precise response. When I started it on a cool evening, it would put out 13.5+ volts for about 15 minutes and then go down to 12.5-13.5 volts for the remainder of the ride. On a warm day, it'd start at 12.5-13.5 volts and pretty much stay there, although rides over several warm days (mebbe 300 miles total) would push it down below 12.5 unless I recharged.

Given that the stator was about the only thing in the charging system I hadn't replaced, and given that the coil had had thermal failure, I bit the bullet and picked up a new stator from David Silver Spares. I made an effort at having my stator rewound, but I was not inspired by the email responses I got.

I installed the stator yesterday and got back today from a 170 mile run in high 80's heat. I had the high beam on all the time, but the voltage never dropped below 13.5 volts, with minor exceptions when I was stuck in traffic (dropped to 12.5-13.5 volts). Unless something goes wrong, I'd call it fixed. I was too pooped when I got back to put it on the MM, so I don't have precise numbers.

Thanks for the help, all, and I do think/hope that concludes my electrical odyssey. :-)

[burmashave]

Arrrrrrrrrrrggggggh! Did you hear me yell at around 7:30 PM EST yesterday? The charging system has reared its ugly, nasty, evil head again.

Since Stator Replacement
I've ridden about 400 miles since the stator replacement, and during this time, the voltage has never dropped below 13.5 volts when the RPM's were above 2,500--even when the high beam has been on for over an hour. During this period, I did not place the battery on the charger.

New Failure
That changed yesterday. After riding about 120 miles of a 150 mile ride, I looked down and I'm now in the 12.5-13.5 volt range at 4,000+ RPM. Joy. By the time I got home, the voltage had dropped to 11.5-12.5 volts at any RPM.

Still a Thermal Issue?
The thing is, it still seems to be a thermal issue. I took my bike out an hour later in the cool (mid 60's F / 18 C) and it was up at 13.5-14.5 volts right from the start.

New Plan: Multiple Multimeters
So my plan of the moment is to test with multiple multimeters as suggested above. I've got 3. I'm going to insert jumpers and simultaneously measure voltage to the coil (white wire from regulator), voltage from the rectifier (black wire at the regulator) and voltage at the battery. I'm also thinking about setting up a switch that will bypass the regulator. I'm not excited about doing it while riding, primarily because I don't want to leave 3 MM's, including my Fluke, in my tank bag if I have to go inside a store.

Review of Repairs
All components and wires (even after wiggling) have bench tested OK. The components in the charging system (wiring harness, regulator, rectifier, battery, coil, stator) are new. This does not eliminate them from failure, though. The failure seems to be thermal related; it does not fail when cool, although something similar, like vibration might cause failure. After heat gun testing the coil, the coil proved to be failing at high temp. The voltage improved when I replaced the coil and then got to spec when I replaced the stator. I have tried to find a loose connection/wire; however, have not found one. I replaced my solder connections with bullets when I replaced the coil and then the stator. Having soldered professionally, I think it unlikely that I could have goofed up several connections, although I've never been happy with the way the connections pack behind the gearbox cover.

Thoughts about Potential Points of Failure
I am tired of opening the alt & gearbox covers; however, I may do so to see if I can do a better job of placing/routing the connections so that there is absolutely no strain on them. Again, these connections were previously soldered. At the moment, I think there may be some strain where the connections are. To be honest, I am tired of shooting in the dark; however, I haven't yet tested anything that pointed to failure.

Another point of failure might be my LED voltage gauge, although it would seem odd that my on-bike gauge would show improvement immediately after coil replacement and further improvement after stator replacement.

I am so bummed. I thought I finally had it licked. On the other hand, I am truly grateful for the help so far. Without it, I would be ready to give up.

[scunny]

just a thought.
since it seems to be thermally related get yourself one of the aerosol sprays that cool components, sorry don't remember what it's called but electronic supply companies will carry it. go for a ride until your problem rears it's ugly head then cool one component at a time to see where your issue lies.

[burmashave]

Capital idea. Thanks, and I'll make sure not to cool anything so quickly as to fracture it.